Methods and apparatus for the downhole characterization of formation fluids

Abstract

Methods and apparatus for investigating a hydrocarbon bearing geological formation traversed by a borehole are disclosed. An example method to characterize a fluid associated with an underground geological formation obtains a sample of the fluid associated with the underground geological formation. The example method measures, in a borehole associated with the underground geological formation, a chemical composition and a thermophysical property of the sample of the fluid. The example method selects a mathematical model to represent the sample of the fluid based on at least one of the chemical composition or the thermophysical property and adjusts a parameter of the mathematical model based on at least one of the chemical composition or the thermophysical property to generate an adjusted mathematical model. The example method then determines a property of the fluid associated with the underground geological formation based on the adjusted mathematical model.

1. A method to characterize a fluid associated with an underground geological formation, comprising:
 obtaining a sample of the fluid associated with the underground geological formation; 
 measuring, in a borehole associated with the underground geological formation, a chemical composition of the sample of the fluid; 
 measuring, in the borehole, a thermophysical property of the sample of the fluid; 
 selecting a mathematical model to represent the sample of the fluid based on at least one of the chemical composition or the thermophysical property; 
 adjusting a parameter of the mathematical model based on at least one of the chemical composition or the thermophysical property to generate an adjusted mathematical model; and 
 determining a property of the fluid associated with the underground geological formation based on the adjusted mathematical model. 
 
   
   
     2. The method as defined in  claim 1 , wherein measuring the chemical composition of the sample of the fluid comprises measuring mole fraction or mass fraction constituents of the sample of the fluid. 
   
   
     3. The method as defined in  claim 1 , wherein measuring the thermophysical property of the sample of the fluid comprises measuring at least one of a density, a viscosity, a heat capacity, a thermal conductivity, a relative electric permittivity, or a refractive index of the sample of the fluid. 
   
   
     4. A method as defined in  claim 1 , wherein measuring the thermophysical property of the sample of the fluid comprises measuring the thermophysical property over at least one of a range of temperatures or pressures to generate a range of thermophysical property values. 
   
   
     5. The method as defined in  claim 4 , further comprising detecting at least one of a phase transition or phase border of the sample of the fluid during the generation of the range of thermophysical property values. 
   
   
     6. The method as defined in  claim 1 , wherein measuring the thermophysical property of the sample of the fluid comprises determining an amount of a chemical added to the sample of the fluid that causes a phase transition of the sample of the fluid. 
   
   
     7. The method as defined in  claim 1 , wherein selecting the mathematical model comprises selecting the mathematical model based on at least one of identifying a type of the sample of the fluid or a chemical composition of the sample of the fluid. 
   
   
     8. The method as defined in  claim 1 , wherein determining the property of the fluid associated with the underground geological formation based on the adjusted mathematical model comprises determining the property of the fluid associated with the underground geological formation at a temperature or a pressure associated with producing fluid from the underground geological formation. 
   
   
     9. The method as defined in  claim 1 , further comprising performing a thermodynamic consistency check prior to adjusting the parameter of the mathematical model. 
   
   
     10. A system to characterize a fluid associated with an underground geological formation, comprising:
 a device to obtain a sample of the fluid associated with the underground geological formation; 
 a first sensor to measure a chemical composition of the sample of the fluid; 
 a second sensor to measure a thermophysical property of the sample of the fluid; and 
 an electronics unit to select a mathematical model to represent the sample of the fluid based on at least one of the chemical composition or the thermophysical property, wherein the electronics unit is to adjust a parameter of the mathematical model based on at least one of the chemical composition or the thermophysical property to generate an adjusted mathematical model, and wherein the electronics unit is to determine a property of the fluid associated with the underground geological formation based on the adjusted mathematical model. 
 
   
   
     11. The system as defined in  claim 10 , wherein the device comprises at least one of a probe or a dual packer. 
   
   
     12. The system as defined in  claim 10 , further comprising a chamber to vary at least a pressure or a temperature of the sample of the fluid. 
   
   
     13. The system as defined in  claim 12 , wherein the electronics unit is to detect at least one of a phase transition or phase border of the sample of the fluid during the varying of the at least the pressure or the temperature of the sample of the fluid. 
   
   
     14. The system as defined in  claim 12 , further comprising a plurality of valves to selectively trap fluid within the chamber. 
   
   
     15. The system as defined in  claim 12 , wherein the chamber is to add an amount of a chemical to the sample of the fluid that causes a phase transition of the sample of the fluid. 
   
   
     16. The system as defined in  claim 10 , further comprising at least one of a temperature sensor or a pressure sensor to measure a temperature or a pressure of the sample of the fluid in a flow-line. 
   
   
     17. The system as defined in  claim 10 , wherein the electronics unit is to select the mathematical model based on at least one of identifying a type of the sample of the fluid or a chemical composition of the sample of the fluid. 
   
   
     18. The system as defined in  claim 10 , wherein the electronics unit is to determine the property of the fluid associated with the underground geological formation based on the adjusted mathematical model by determining the property of the fluid associated with the underground geological formation at a temperature or a pressure associated with producing fluid from the underground geological formation. 
   
   
     19. The system as defined in  claim 10 , wherein the electronics unit is to perform a thermodynamic consistency check prior to adjusting the parameter of the mathematical model. 
   
   
     20. The system of  claim 10 , wherein the device is configured to be deployed within a borehole that penetrates the geological formation via wire-line or drill pipe.